<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>



<script>
    window.alert("hello js~");//写入警告框
    document.write("hello js 2~");//写入html页面
    console.log("hello js 3");//写入浏览器的控制台
</script>
</body>
</html>